Obtaining copper cathodes on a large scale is a process known in the state of the art. This process, to be profitable, is intensive for large volumes of material to be obtained. The basis of this process is one used for the first time in south Wales in 1869, where electrorefining was tested as a purification process for metallic copper that is carried out in electrolytic cells and consists of the application of an electric current to dissolve impure copper. In this way, the purest possible electrolytic copper is obtained, with 99.99% purity, which permits its utilization as an electric conductor, among other applications. Chile is one of the principle producers and refiners of copper in the world.
The total process for electrowinning copper is known by the technicians in this subject and operates as follows: it starts with the crushing of the material (CH), then comes the agglomeration process (AG), this is followed by the lixiviation process (LX), followed by the extraction by solvents (SX), to end, finally, with the electrowinning (EW), to end with the obtaining of a copper cathode.
The stages presented previously, in that order, reveal the known process. Each one of the stages, individually, has its own technical problems, of which we wish to highlight those that are presented below.
The Electrowinning (EW) stage in itself, is a stage that requires devices with specific electrical and volumetric capacities in order to obtain copper cathodes, especially when the copper solution is not concentrated in a previous stage of extraction by solvents.
On the other hand, the traditional electrowinning (EW) stage has always been executed at a fixed location due to the large number of equipment, electrical support, intensive process and handling of high tonnages of material that this operation requires.
The electrolytic extraction processes (EW) are generally carried out in undivided electrochemical cells that contain an electrolytic bath (with a high concentration of copper previously extracted by solvents) and a multiplicity of anodes and cathodes. In such processes, such as for example the electroplating of copper, the electrochemical reaction that takes place in the cathode (manufactured in stainless steel), conducts the deposition of copper in metallic form on the cathode itself. The anode, generally manufactured of lead, is consumed slowly forming the anodic sludges and producing gaseous oxygen, as residual elements (WO2013/060786).
In general, what is known by the state of the art mentions that this type of process uses continuous current in parallel through each anode-cathode pair, as mentioned in patent WO 2013117805. In fact, rectifiers are used to compensate the system's direct current input with the current the electrochemical process on its own requires.
Another of the common stages of the total process in electrowinning, but prior to subjecting the electrolyte to the current, is the ore enrichment or concentration stage by extraction of same with solvents, a stage also called Pregnant Leach Solution (PLS). This stage is necessary to reach a copper concentration in the electrolyte of about 7 to 48 g/L of electrolyte. These concentrations are necessary to make the electrowinning process economically viable in medium and large-scale mining.